1. Direct search of dark matter in Asia
Hesheng Chen
Inst. of High Energy Physics
Beijing , China
Outline
1. Japan: XMASS
2. Korea: KIMS
3. China
CDES
PANDAX
R&D at IHEP
4. Remarks

2. 1. Japan: XMASS collaborations
Kamioka Observatory, ICRR, Univ. of Tokyo：
Y. Suzuki, M. Nakahata, S. Moriyama, M. Yamashita, Y. Kishimoto,
Y. Koshio, A. Takeda, K. Abe, H. Sekiya, H. Ogawa, K. Kobayashi,
K. Hiraide, A. Shinozaki, S. Hirano, D. Umemoto, O. Takachio, K. Hieda
IPMU, University of Tokyo： K. Martens, J.Liu
Kobe University: Y. Takeuchi, K. Otsuka, K. Hosokawa, A. Murata
Tokai University: K. Nishijima, D. Motoki, F. Kusaba
Gifu University： S. Tasaka
Yokohama National University： S. Nakamura, I. Murayama, K. Fujii
Miyagi University of Education： Y. Fukuda
STEL, Nagoya University： Y. Itow, K. Masuda, H. Uchida, Y. Nishitani, H. Takiya
Sejong University： Y.D. Kim
KRISS: Y.H. Kim, M.K. Lee, K. B. Lee, J.S. Lee
41 collaborators,
10 institutes

3. XMASS experiment
●XMASS
◎ Xenon MASSive detector for Solar neutrino (pp/7Be)
◎ Xenon neutrino MASS detector (double beta decay)
◎ Xenon detector for Weakly Interacting MASSive Particles (DM search)
It was proposed that Liquid xenon was a good candidate to satisfy scalability and low background.
As the first phase, an 800kg detector for a dark matter search was constructed.
10ton FV (24ton) 2.5m
Solar n, 0nbb, DM
in future
100kg FV (800kg)
0.8m, DM
First phase
Y. Suzuki, hep-ph/

4. Structure of the 800kg detector
Single phase liquid Xenon (-100oC, ~0.065MPa) scintillator
835kg of liquid xenon, 100kg in the fiducial volume
630 hex +12 round PMTs with 28-39% Q.E. are in LXe.
photocathode > 62% inner surface
Pentakis dodecahedron
Interaction position reconstruction
5keVelectron equiv. (~25keVnuclear recoil) thre.
1.2m diameter
Developed with Hamamatsu

5. Expected sensitivity for 50-100GeV WIMP, 90%C.L. scp>2x10-45 cm2
Spin Independent
scp>2x10-45 cm2
for GeV WIMP, 90%C.L.
1yr exposure, 100kg FV,
BG: 1x10-4 /keV/d/kg
Scintillation efficiency: 0.2
CDMSII
XENON100
Expected energy spectrum
XMASS 1yr
1 year exposure
scp=10-44 cm2
50GeV WIMP
Black:signal+BG
Red:BG

6. クリックしてタイトルを入力
クリックしてテキストを入力
As of Sep. 2010
P-01

7. Demonstration of the detector performance
Calibration system
Introduction of radioactive sources into the detector.
<1mm accuracy along the Z axis.
Thin wire source for some low energy g rays to avoid shadowing effect.
57Co, 241Am, 109Cd, 55Fe, 137Cs..
Stepping
Motor
Linear
Motion
Feed-
through
~5m
Gate
valve
Source rod with a dummy source
0.15mmf for 57Co source
Top
photo
tube
4mmf

8. XMASS summary
The XMASS 800kg detector aims to detect dark matter with the sensitivity 2x10-45cm2 (spin independent case).
It utilizes a single phase of LXe target.
Construction of the 800kg detector finished last winter.
Commissioning runs are on going to confirm the detector performance and low background properties.
Energy resolution and vertex resolution were as expected. ~1cm position resolution and ~4% energy resolution for 122keV g.
Radon background are close to the target values and Kr contamination will be evaluated soon.

9. 2. Korea: YangYang UGL(Y2L)
Located in a tunnel of
Yangyang Pumped Storage Power Plant
Korea Middleland Power Co.
Minimum vertical depth : 700 m
Access to the lab by car (~2km)
Experiments:
KIMS: DM search exp. in operation
AMoRE: DBD Search exp. in preparation
(additional laboratory space in design)
(Upper Dam)
(Power Plant)
(Lower Dam)

10. KIMS(Korea Invisible Mass Search)
DM search experiment with CsI crystal
CsI(Tl) Crystal 8x8x30 cm3 (8.7 kg)
3” PMT (9269QA) : Quartz window, RbCs photo cathode
~5 Photo-electron/keV
SD interaction
PRL 99, (2007)
12 crystals(104.4kg) running
Stable data taking for more than a year
Unique experiment to test DAMA annual modulation
Best limit on SD interactions
in case of pure proton coupling

11. New result on WIMP search Preliminary
~ 1 year data, Total exposure: kg days SI SD
AM analysis after full 2 year data collection : ~ end of Aug.

12. KIMS(Korea Invisible Mass Search) coll.
H.C.Bhang, J.H.Choi, S.C.Kim, S.K.Kim
J.H.Lee, M.J.Lee, S.J.Lee, S.S.Myung
Seoul National University
U.G.Kang, Y.D.Kim, J.I. Lee
Sejong University
H.J.Kim, J.H.So, S.C.Yang
Kyungpook National University
M.J.Hwang, Y.J.Kwon
Yonsei University
I.S.Hahn
Ewha Womans University
Y.H.Kim, K.B.Lee, M. Lee
Korea Research Institute of Standard Sciences
J.Li
Institute of High Energy Physics
Y.Li, Q.Yue
Tsinghua University

13. China
3.1 CDEX: China Darkmatter EXperiment

19. CDEX:

20. 3.2 PANDA-X Dark Matter Search
Originally PANDA was intended to be a complement of the XENON100 detector.
However, before the design started the liaison was cut, and the design in nearly all details is entirely different and originally developed at Jiao Tong.
The Panda team:

21. PANDA-X Dark Matter Search
Improvements over XENON100:
Less background due to deeper site
Multiple Gamma and Neutron events in larger detector
Better Gamma – Neutron band separation (higher E – Field)
Enhanced light collection
Reduced amount of Teflon
Larger distance of Bottom PMT to Active Volume
But,
No active Veto (unnecessary)

22. PANDA-X Dark Matter Search
Improvements over XENON100:

23. PANDA-X Projected Sensitivity

24. PANDA-X Dark Matter Search
Schedule:
Civil engineering of underground lab completed
Major items ordered, incl. the vessels, cryogenic system, read out electronics, PMTs
Most of the equipment is expected in June
Surface lab at SJTU preparation completed
Surface tests of entire set up to start in June
Installation of shield underground is about to start
Counting facility to be assembled first
Underground installation of detector will start before year end

25. 3.3 R&D at IHEP for next generation
experiment: Crystal CsI (Na)
n/g Separation (NIM A642(52-58), 2011)

27. n/gamma separation is getting better for higher energy （NIM A491(2002) 460）27

28. CINDMS: CsI(Na) Dark Matter Search
Single large crystal + PMT readout
特点:
波形测量和3D重建事例位置;
实现探测器自屏蔽外来低能本底;
排除晶体的表面效应事例对核反冲信号的污染;
大晶体可标记中子多次作用事例，压低中子本底。
CsI(Na) 晶体本身具有独特的n/分辨性能，截面大，密度高，价格便宜，适合建造大质量探测器。

29. Another design
Veto
PMTs
Crystal
Liquid 29

30. Advantage of new design
The mass of detector could be large by piling up several crystals （~ton 60x60x60cm^3）；
Thick enough liquid shielding can reduce outside background including PMT background;
Trigger by coincident of several PMTs could reduce PMT noise；
Main background will be radioactivity of crystal itself；
Higher reflector for PMT uncovered area;
More photon could be possible collected by 4π PMT coverage (compared with DAMA），lower threshold and better energy resolution would expected ；
Possible replace different crystal。
Good experiences from DayaBay reactor ν exp. 30

31. Remarks
There is a long history of deep underground experiments in Japan.
KIMS in Korea: data taking
Taking advantages of Jinping UGL, dark matter direct search experiments in China try to catch up. R&D for next generation experiments are also under way.
Next generation experiments require
Larger mass
New technology: more sensitive, less BG
Deeper UGL
More cooperation are essential to meet great challenges in the dark matter search experiments.
Thank S. Moriyama, S.K.Kim, C.G. Yang for Slides.